1. Technical Field
The present disclosure relates to impedance matching devices, and particularly to an impedance matching device for memory signals of a motherboard.
2. Description of Related Art
Impedance matching is an electronics design practice of setting an input impedance of an electrical load equal to a fixed output impedance of a signal source to which it is ultimately connected, usually in order to maximize power transfer and minimize signal reflections from the electrical load.
Double data rate (DDR) 2 memory and DDR3 memory are both random access memory interface technology used for high bandwidth storage of working data of a computer or other digital electronic devices. DDR3 memory is an improvement over its predecessor, DDR2 memory, and the two are not compatible. A signal impedance matching method for the DDR2 memory is to connect signal pins of the DDR2 memory to a 0.9 volt (V) power supply via resistors. However, the DDR3 memory includes an inner impedance matching circuit. Signal pins of the DD3 memory are connected to a 0.75V power supply via the inner impedance matching circuit.
Installation of the DDR2 memory or the DDR3 memory to a motherboard capable of supporting both is the same, which means that signal pins of a memory socket for installing the DDR2 memory are used for the DDR3 memory to connect to a 0.9V power supply via resistors. Therefore, when the DDR3 memory is installed in the memory socket of the motherboard, signals of the DDR3 memory are impedance matched twice, once via the inner impedance matching circuit and again through the resistors, which results in reduced reliability of the signals of the DDR3 memory.